Going to look at a boat with these drives, is there anything to check for on them?

Not much to check other than then turn smooth that i know of. check for pitting and what not on the propshafts? They are good drives

Unscrew the bottom oil drain plug, and make sure only good oil comes out. If there is water, you've got bad seals, which could mean trashed lower.

Also pull side to side on the drive leg checking for free play in the trim pins. The old III trim pin design is junk. I have retrofitted three different III gimbals with IIIA style trim pins, and it works great. Those are bombproof. If you have this issue, contact me and I can tell you how to do it, or you can send me the gimbal and bellhousing, and I can do the machining for cheap + parts. My mill needs to be run anyway.